Sharecropping is when the owner of certain land rents it out to people and in exchange will ask them for part of the crop they produce. This is beneficial for both the tenant and the renter, as they both are producing crops and ultimately earning money.
During the Great Depression, farmers were doing poorly. Since nobody had money to spare, a lot of crops were not selling. The prices had also dropped because there was an abundance of crops and nobody was buying them. Farmers were also starting to pay for items using installments, along with a lot of people during this time. This is where you pay for a product over a period of time. This caused some farmers to buy a lot of expensive and big products, like farm equipment, with installment plans. Then since they weren't selling crops, they couldn't pay for the items.
With the farmers struggling, they really did not need sharecroppers or helpers on their land anymore. The sharecroppers could not afford to stay there either, as the crops were not selling. A lot of sharecroppers had to leave and try to find work elsewhere.